Examine source code of Stopwatch Fun

{
  "manifest_version": 2,
  "name": "Stopwatch Fun",
  "version": "1.0",
  "description": "StopWatch will have the Start, Stop, and Reset functionality.",
  "permissions": [],
  "browser_action": {
    "default_popup": "game.html",
    "default_icon": {
      "128": "images/timer-logo.png"
    }
  },
  "icons": {
    "128": "images/timer-logo.png"
  },
  "browser_specific_settings": {
    "gecko": {
      "id": "{e75c3b4e-9e06-4d93-81c9-2acad97f57b4}"
    }
  }
}